Abstract: The purposes of the study were to evaluate the applicability of the peer cluster model and the primary socialization model, developed based upon peer cluster theory and primary socialization theory respectively, to White, African American, Latino, Asian, and Southeast Asian adolescents, and to examine race/ethnic variations in associations between peer, parental, school, and neighborhood influences and adolescent substance use. The sample included 5,992 adolescents (5,185 White, 330 African American, 160 Latino, 179 Asian, and 138 Southeast Asian) from Dane county, Wisconsin, and all data were collected via adolescent-report surveys. Results from Structural Equation Modeling analyses indicated that the peer cluster model only demonstrated adequate fit in the Asian and Southeast Asian subsamples, whereas the primary socialization model fit well in each ethnic group. When compared, the primary socialization model demonstrated superior fit to the data in all groups than did the peer cluster model except for Southeast Asian adolescents. Results also revealed significant moderation effects of ethnicity in associations between contextual influences and adolescent substance use. Results contributed to previous research by considering multiple contextual influences simultaneously to understand processes related to substance use of adolescents from multiple ethnic groups.